“Mysterious” plane circling over Denver was “just” an E-6B Mercury “doomsday” plane

Photos and video of a “mysterious” plane circling over Denver are making the rounds. But the aircraft was “just” a U.S. Navy Doomsday plane.

On Nov. 16 people in the Denver metropolitan area saw a white, four-engined aircraft performing a racetrack for several times over Colorado before heading to Oklahoma. The aircraft could be tracked online on Flightradar24 by means of ADS-B using callsign Iron 99.



Even though some media outlets published some funny articles with headlines referring to a “mystery flight” or a “mysterious plane” there is really little mystery around that aircraft: it was an E-6B Mercury.

The use of “Iron 99” is also pretty standard: Iron is one of the radio callsigns of the VQ-3 “Ironmen”, a naval aviation squadron of the United States Navy based at Tinker Air Force Base, Oklahoma (incidentally, where the aircraft headed after orbiting over Denver….)

Built on the Boeing 707 airframe and using a B737 cockpit, the E-6B aircraft has a range of 5,500 miles, and accommodates 23 crew members.


The U.S. Navy has a total fleet of sixteen E-6B Mercury (TACAMO – “TAke Charge And Move Out”) that play an extremely important role for U.S. National Security: they are used to relay instructions to the fleet ballistic missile submarines in case of nuclear war but also act as back ups of the four E-4Bs NAOC (National Alternate Operations Center), working as ABNCP (Airborne Command Post) platforms (hence “Doomsday Plane“).

They are often trackable online, while performing various critical missions: the so-called Looking Glass mission (mirroring the ground-based C3 center at Offutt AFB and relaying orders); talking to submarines trailing a 26,000 ft wire antenna; launching commands to ICBMs (InterContinental Ballistic Missiles) via Airborne Launch Control System, and performing C3 (Command Control Communication) operations to forces operating in theater or to the U.S. strategic bombers flying Global Strike missions.

The Mercury is capable to communicate on virtually every radio frequency band, on commercial satellites and on the Internet, using also a secure VOIP system. This aircraft usually operates flying orbits/circles while trailing their antennas or to exploit a particular geostationary satellite for radio comms.

Noteworthy, on Aug. 27, the E-6B 163918 used the very same callsign Iron 99.

Screenshot from Global ADSB Exchange showing E-6B using callsign Iron 99 on Aug. 27, 2016
Screenshot from Global ADSB Exchange showing E-6B using callsign Iron 99 on Aug. 27, 2016

Interestingly, on Mar. 8, 2016 an E-6B 162784 used the callsign “Trump” for the first time.

Top image credit: screenshot from ABC. Rest of images: screenshots from Flightradar24.com


About David Cenciotti
David Cenciotti is a journalist based in Rome, Italy. He is the Founder and Editor of “The Aviationist”, one of the world’s most famous and read military aviation blogs. Since 1996, he has written for major worldwide magazines, including Air Forces Monthly, Combat Aircraft, and many others, covering aviation, defense, war, industry, intelligence, crime and cyberwar. He has reported from the U.S., Europe, Australia and Syria, and flown several combat planes with different air forces. He is a former 2nd Lt. of the Italian Air Force, a private pilot and a graduate in Computer Engineering. He has written five books and contributed to many more ones.